Maintenance feature in magnetic implant

Abstract

A distraction system includes a distraction rod having one end configured for affixation to at a first location on patient. The system further includes an adjustable portion configured for placement in the patient at a second location, the adjustable portion comprising a housing containing a magnetic assembly comprising a magnet, the magnetic assembly secured to a threaded element that interfaces with an opposing end of the distraction rod. The system includes a magnetically permeable member in proximity to the magnetic assembly and covering an arc of less than 360° of the adjustable portion.

What is claimed is: 
     
       1. A distraction system comprising:
 a distraction rod having a first end configured for placement within a patient at a first location and a second end having a threaded portion; 
 an adjustable portion configured for placement within the patient at a second location, the adjustable portion comprising a driving element configured to be non-invasively rotated, the driving element rotationally coupled to a lead screw, the lead screw threadingly engageable with the threaded portion of the distraction rod; and 
 a maintenance member in proximity to but physically isolated from the driving element, wherein the maintenance member is configured to substantially maintain circumferential orientation of the driving element when a torque of 0.81 Newton-meter is placed between the distraction rod and the adjustable portion. 
 
     
     
       2. The distraction system of  claim 1 , wherein the driving element comprises a magnet having at least one pole and wherein the maintenance member comprises a magnetically permeable member configured to attract the at least one pole of the magnet when the at least one pole of the magnet is in proximity to the magnetically permeable member. 
     
     
       3. The distraction system of  claim 2 , wherein the magnetically permeable member covers an arc of less than 360° of the adjustable portion. 
     
     
       4. The distraction system of  claim 3 , wherein the magnetically permeable member covers an arc of less than 180° of the adjustable portion. 
     
     
       5. The distraction system of  claim 1 , wherein the maintenance member comprises a ferrous material. 
     
     
       6. A distraction system comprising:
 a distraction rod having a first end configured for placement within a patient at a first location and a second end having a threaded portion; 
 an adjustable portion configured for placement within the patient at a second location, the adjustable portion comprising a driving element configured to be non-invasively rotated, the driving element rotationally coupled to a lead screw, the lead screw threadingly engageable with the threaded portion of the distraction rod; and 
 a maintenance member which does not contact the driving element throughout a full rotation of the driving element, wherein the maintenance member is configured to substantially inhibit rotation of the driving element when a torque of 0.81 Newton-meter is placed between the distraction rod and the adjustable portion. 
 
     
     
       7. The distraction system of  claim 6 , wherein the driving element comprises a magnet having at least one pole and wherein the maintenance member comprises a magnetically permeable member configured to attract the at least one pole of the magnet when the at least one pole of the magnet is in proximity to the magnetically permeable member. 
     
     
       8. The distraction system of  claim 7 , wherein the magnetically permeable member covers an arc of less than 360° of the adjustable portion. 
     
     
       9. The distraction system of  claim 8 , wherein the magnetically permeable member covers an arc of less than 180° of the adjustable portion. 
     
     
       10. The distraction system of  claim 6 , wherein the maintenance member comprises a ferrous material. 
     
     
       11. A distraction system comprising:
 a distraction rod having a first end configured for placement within a patient at a first location and a second end having a threaded portion; 
 an adjustable portion configured for placement within the patient at a second location, the adjustable portion comprising a driving element configured to be non-invasively rotated, the driving element rotationally coupled to a lead screw, the lead screw threadingly engageable with the threaded portion of the distraction rod; and 
 a maintenance member physically isolated from the driving element, wherein the maintenance member is configured to substantially maintain circumferential orientation of the driving element when a torque of 0.81 Newton-meter is placed between the distraction rod and the adjustable portion. 
 
     
     
       12. The distraction system of  claim 11 , wherein the driving element comprises a magnet having at least one pole and wherein the maintenance member comprises a magnetically permeable member configured to attract the at least one pole of the magnet when the at least one pole of the magnet is in proximity to the magnetically permeable member. 
     
     
       13. The distraction system of  claim 12 , wherein the magnetically permeable member covers an arc of less than 360° of the adjustable portion. 
     
     
       14. The distraction system of  claim 11 , wherein the maintenance member comprises a ferrous material. 
     
     
       15. A distraction system comprising:
 a distraction rod having a first end configured for placement within a patient at a first location and a second end having a threaded portion; 
 an adjustable portion configured for placement within the patient at a second location, the adjustable comprising a driving element configured to be non-invasively rotated, the driving element rotationally coupled to a lead screw, the lead screw threadingly engageable with the threaded portion of the distraction rod; and 
 a maintenance member which does not contact the driving element throughout a full rotation of the driving element, wherein the maintenance member is configured to substantially inhibit rotation of the driving element when a torque of 0.81 Newton-meter is placed between the distraction rod and the adjustable portion, wherein the maintenance member is in proximity to the driving element.